Aqueous slurry type explosive compositions sensitized with at least one alkanolamine nitrate



United States Patent AQUEOUS SLURRY TYPE EXPLOSIVE COMPOSI- TIONS SENSITIZEI) WITH AT LEAST ONE ALKA- N OLAMINE NITRATE Harry R. Fee, Hopatcong, N.J., and Robert W. Lawrence, Wilmington, DeL, assignors to Hercules Incorporated, Wilmington, Del., a corporation of Delaware No Drawing. Filed June 23, 1967, Ser. No. 648,203

20 Claims. (Cl. 149-38) ABSTRACT OF THE DISCLOSURE Inorganic oxidizer salt explosives of the aqueous slurry type, preferably nitrocarbonitrates, are provided which contain as a sensitizer component, at least one alkanolamine nitrate of the group of ethanolamine nitrates, and propanolamine nitrates, and, optionally, a supplemental sensitizer.

This invention relates to inorganic oxidizer salt explosive compositions of the aqueous slurry type containing a selected alkanolamine nitrate or a mixture of such nitrates as a sensitizer component.

Inorganic oxidizer salt explosive, or blasting, compositions of the aqueous slurry type have had wide use in the explosives industry in recent year. These compositions comprise an inorganic oxidizer salt, water, a sensitizer, and, generally, a thickening agent in at least an amount to impart sufficient consistency to the slurry to prevent settling of any of the various ingredients.

Various sensitizer materials have been utilized in these compositions, including smokeless powder as disclosed and claimed in U.S. 3,235,425, and particulate metals and high explosives, such as TNT and/or aluminum as disclosed and claimed in US. 2,930,685.

In accordance with the invention, inorganic oxidizer salt explosive compositions of the aqueous slurry type are provided which contain a sensitizing amount, generally from 3 to 30 weight percent, or any suitable amount outside that range, of at least one alkanolamine nitrate selected from the group consisting of ethanolamine nitrates and propanolamine nitrates as a sensitizer component. The compositions of the invention generally comprise (weight basis) from 8 to 25 percent water, from 40 to 75 percent of the inorganic oxidizer salt component, the above described sensitizer component, and a thickener, the latter usually in an amount of from 0.2 to 5 percent.

In preferred practice, the alkanolamine nitrate sensitizer component of the invention, is incorporated into the explosive composition as aqueous product of reaction of the particular alkanolamine, or alkanolamine mixture with nitric acid, at ambient room temperature, say from 6 0 to 80 F., the water content of the aqueous product contributing to the overall water content of the finished composition. The practice of this embodiment imparts a pH to the resulting aqueous explosive composition mixture over a broad range, dependent upon the relative proportions of nitric acid and alkanolamine reactants, generally from 3 to 7 and more often from 4 to 6. In the practice of this embodiment, however, it is generally preferred that the alkanolamine reactant, or reactants, be substantially neutralized by the nitric acid. This is particularly advantageous when utilizing guar gum with a cross-linking agent, as a thickener, from the standpoint of the desired degree of crosslinking of the guar gum thickener and the stability of the resulting cross-linked product (gel) that can be obtained under those pH conditions.

Although preferred proportions of the alkanolamine nitrate sensitizer component in the aqueous slurry explosives compositions of the invention are as low as about 3 percent they are more often in the order of from about 10 to 25 percent. However, smaller proportions of the alkanolamine nitrate sensitizer, say from 3 to 10 percent, are often advantageously utilized, and particularly so in the presence of a supplemental sensitizer and/or when the density of the slurry explosive composition is somewhat lower than its maximum. It is, however, within the scope of the invention to utilize any suitable sensitizin-g amount of the alkanolamine nitrate sensitizer component with a supplemental sensitizer and/or under the above said lower density conditions.

Exemplary of materials that can serve as suitable supplemental sensitizers are metals such as aluminum and magnesium-aluminum alloys, and coal, all in finely divided form, hydrocarbon oils, dinitrotoluene and the like flaked aluminum as at least part of the aluminum supplemental sensitizer being now preferred. The amount of supplemental sensitizer utilized with the alkanolamine nitrate sensitizer component, in the practice of the invention, depends somewhat on the particular supplemental sensitizer material, but it is generally within the range of from about 1 to 10 percent, although it can be as high as about 16 percent; from 3 to 7 percent being often utilized, particularly when the supplemental sensitizer is a particulate aluminum preferably at least part of which is in flake form, say at least about 5 percent.

By the term maximum density it is meant that density of the slurry explosive composition, exclusive of a gas, as compared with a lower density such as that obtained as the result of entrainment of air during normal mixing procedures, or when the density is regulated to a predetermined decreased level by incorporation of a gas into the composition for that purpose, such as disclosed and claimed in U.S. Patents 3,288,658 and 3,288,661 and in the copending applications Ser. Nos. 607,259 and 607,261, each filed Jan. 4, 1967.

When referring herein to aqueous slurry explosive compositions having a density below the maximum, such a density of from about 30 to about 95 percent, often from 50 to and preferably from 70 to 90 percent of the maximum is contemplated. Thus a slurry explosive composition of the invention when utilized at a density below its maximum, say 1.50 grams per cc. will preferably be in the order of from about 1.05 to 1.35 grams per cc. Any suitable gas can be incorporated into the blasting composition for purpose of regulating density thereof, e.g. carbon dioxide, air, nitrogen, and the like; and in any suitable manner, as by direct injection or by in situ formation as described in the above referenced U.S. patents and applications for patent.

Further illustrative of the alkanolamine nitrate sensitizer components of the aqueous slurry compositions of the invention are ethanolamine nitrates-Z-hydroxyethylamine nitrate, bis (2-hydroxyethyl)amine nitrate, tris (2-hydroxyethyl)amine nitrate; and propanolamine nitrates-Z-hydroxypropylamine nitrate, bis (Z-hydroxypropyl)amine nitrate, tris (2-hydroxypropyl)amine ni trate, 3-hydroxypropylamine nitrate, bis (3-hydroxypropyl)amine nitrate, tris (3-hydroxypropyl)amine nitrate, 1-(hydroxymethyl)ethylamine nitrate, bis[1-(hydroxymethyl)ethyl]amine nitrate and tris [l-(hydroxymethyl)ethyl]amine nitrate, and mixtures of any two or more of the above alkanolamine nitrates. Now preferred alkanolamine nitrate sensitizer components are tris (2- hydroxyethyl) amine nitrate, (triethanolamine nitrate) nitrate, and either or both of tris (2-hydroxypropyl) amine nitrate and tris [1-(hydroxymethyl)ethyl]amine nitrate (tripropanolamine nitrates), or mixtures of alkanolamine nitrates, as a sensitizer component of the invention, containing one or more thereof.

The now preferred slurry type explosive compositions of the invention contain (weight basis) from 12 to 20 percent water, the alkanolamine nitrate sensitizer in an amount as above described, from 40 to 65 and from to 20 percent respectively, of ammonium nitrate and sodium nitrate as the oxidizer salt, and from 0.3 to 2.0 percent guar gum, generally in cross-linked form, as a thickener.

By the term inorganic oxidizer salt, as is well known in the explosives art, is meant one which under the conditions of the detonation liberates oxygen for combustion of the fuel required. Although ammonium nitrate alone, or with sodium nitrate, is in most instances the inorganic oxidizer salt component, other inorganic oxidizer salts or mixtures thereof can be used alone or with ammonium nitrate, often supplemental to ammonium nitrate. Alkali metal nitrates are now preferred as supplemental oxidizer salts with ammonium nitrate. Generally, when ammonium nitrate is utilized with a supplemental salt, it comprises a major proportion of the total oxidizer salt, i.e. at least 50 percent of the total. Exemplary inorganic oxidizer salts that can be used alone, or together with ammonium nitrate, are alkali metal and alkaline earth metal nitrates and perchlorates (including ammonium) as, for example, sodium nitrate, magnesium nitrate, calcium nitrate, potassium nitrate, barium nitrate, sodium perchlorate, ammonium perchlorate, calcium perchlorate and magnesium perchlorate.

Particle size and type of the oxidizer salt ingredient are not generally critical. For example ammonium nitrate can consist of prills such as used in fertilizers and which are substantially all on 20 mesh, or it can be granular and in that form, vary from coarse to fine. Other oxidizer salt ingredients are generally of comparable particle size. However, when desired, any or all of the oxidizer salt component can be added to the formulation in aqueous solution.

The amount of thickener is dependent upon the particular thickener and the desired consistency of the finished composition. Generally, a thickener content up to about 5 percent and more often not exceeding about 2 percent is sufficient. When the thickener content is within the range of 0.2 to 0.5 percent, there is generally sufiicient thickening to prevent settling of the composition ingredients, although additional thickener is often required in order to impart a satisfactory degree of cohesiveness so that the composition retains its form as a unit mass, preferably plastic but deformable. Exemplary thickeners, in addition to guar gum which is now preferred, are sodium carboxymethylcellulose, Karaya gum, watersoluble starches, locust bean meal, cereal products and the like.

The compositions of the invention are generally in sensitive to detonating action of a No. 8 commercial blasting cap but are, in all events, detonatable by conventional booster charges of PETN (pentaerythritol tetranitrate), RDX (cyclotrimethylene-trinitramine), Pentolite (PETN-TNT, 50/50), tetryl Composition B (RDX-TNT, 60/40), and the like. One booster advantageously employed is a dispersion of a crystalline high explosive, e.g. PETN or RDX in a plastic carrier such as described in US. 2,965,466, and which is detonated by either a commercial blasting cap or a detonating fuse. A now preferred booster comprises a cast cylindrical body of capand fuse-insensitive explosive, and a tube assembly within the cast body, containing cap-sensitive crystalline high explosive together with structure for support of initiator means therefor, as disclosed and claimed in US. 3,212,438.

In preferred practice, the explosive compositions of the invention are of the well-known class of nitrocarbonitrates, by which term it is meant there are no ingredients which in themselves are classified as high explosives, and the mixtures will not detonate with a No. 8 blasting cap when packed for shipment.

The invention is further illustrated with reference to the formulations in the following tabulation:

Weight percent Formulation Water 20. 0 16.0 19. 1 18.0 Monoethanolamine nitrate 23. 2 18.3 Diothanolamine nitrate 1 19.1 Tricthanolaminc nitrate 1 11. 4 Ammonium nitrate 46. 1 44. 4 49. 3 49. 3 Sodium nitrate 9. 5 15.0 11.0 15.0 Aluminum 5.0 5.0 Guar gum 1.2 1.3 1.5 1.3 Detonation rate, in. 5, 250 5, 000 5, 250 5, 250 Density, grams/co:

Actual 1.11 1. 00 1. 14 1. 27

Maximum 7 1. 4 1. 5 1. 4 1. 5 pH 5.8 5.4 5.7 5.9

Formed by substantially neutralizing the alkanolamine with 60 percent nitric acid at ambient room temperature and addition of the total resulting reaction mixture to the formulation as the alkanolamine nitrate shown. Water content, of each neutralization reaction mixture, is included in the water content shown for the formulation.

.Zhydroxyethylamine, Nos. 1 and 2; bis(Z-hydroxyethylamme), No. 3: and tris(Z-hydroxyethylamine), No. 4. 70 percent nitric acid in lieu of 60 percent nitric acid for No. 4.

2 Prills.

3 Granularto coarse.

4 Granular, Run No. 2; flaked, Run No. 4.

Substantially all through 30 mesh; 10 percent on 100 mesh.

0 Made from chopped foil substantially all 1 mil thickness or less; approximately 50 percent on 20 mesh and 50 percent through 10 mesh.

5 Cross-linked.

5 Measured as average detonation velocity over a 20 cm. length, at the end of a 28" long column of explosive. The explosive 1S confined in 5 diameter (nominal) black iron pipe (Schedule The time for detonation to proceed across the 20 cm. length of explosive is measured electronically by means of a counter-chronograph. In all instances the dctona tion was initiated by a 475-grani Pentolite booster charge. All formulations Were initiated with a 475-gram Pentolite booster cliarge.

1 Actual density in each instance below maximum density due to presence of air incorporated during manufacture and packaging of the formulation.

The above formulations demonstrate monoethanolamine nitrate, diethanolamine nitrate and triethanolamine nitrate as sensitizer components of the compositions of the invention, i.e. as sole sensitizer (Examples 1 and 3) and also in conjunction with aluminum as a supplemental sensitizer (Examples 2 and 4). Excellent detonation rates were obtained in all instances.

Any suitable process can be utilized for the manufacture of the aqueous slurry compositions of the invention. In one such embodiment, at least a portion of the thickener ingredient is added to, and admixed with, the :water to impart sufiicient consistency to prevent settling of subsequently added ingredients. The alkanolamine nitrate sensitizer is then incorporated into the slurry, in isolated form, or by adding HNO and alkanolamine reactant to form the sensitizer in situ, as with the thus-thickened water ingredient. At least a major portion of the oxidizer salt ingredient is then added to the resulting mixture, advantageously reserving a minor portion for addition with any remaining portion of thickener to be added. Any remaining portion of thickener is then added to the slurry mixture together with any remaining portion of the oxidizer salt ingredient. After all thickener is added, stirring is continued, preferaby at a temperature of to 100 F. for a period of, say, 2 to 10 minutes to form the final product.

In another process embodiment for the manufacture of the aqueous slurry composition of the invention, a mixture of water, ammonium nitrate and sodium nitrate is prepared, preferably at a temperature in the to F. range although this can be varied widely beyond these limits. The pH is adjusted to a range between 3 and 6 and the guar gum is added and allowed to dissolve and hydrate. If borax is to be used as a cross-linking agent the pH is increased to the 6 to 7 range and a very small amount of borax (e.g., 0.01 percent) is added. Alternatively, the pH is adjusted to the 4 to 5 range and potassium dihydrogen antimonate (about 0.04 percent) is added to cause the guar gum to cross-link. If aluminum is used in the formulation it is added before the crosslinking agent. The rate of cross-linking may be adjusted by controlling the pH and the amount of cross-linking agent. For borax, the rate of cross-linking is speeded by a higher pH (67) and for the potassium dihydrogen antimonate by a lower pH (ca. 4).

In accordance with now preferred practice, guar gum is utilized as the thickener, preferably in cross-linked form. It is added to the blasting slurry-forming mixture initially in hydratable form so as to become hydrated and, as a hydrate, impart suflicient increase in viscosity to hold all ingredients in suspension during mixing and handling of the slurry. The initial portion of hydratable guar gum is advantageously added to the water ingredient in admixture with about five times its weight of the oxidizer salt ingredient. The remaining and major portion of the guar gum to be added is cross-linkable and is added with the remaining, and minor, portion of oxidizer salt with agitation to form the final product. The last added guar gum is in inhibited form, is. it contains an agent causing a delay in hydration that would otherwise take place immediately, The delay or, inhibition, postpones hydration of the last added guar gum so as to permit time for packaging, or emplacement, of the final product mixture while still easily flowable, with final hydration and cross-linking subsequently taking place.

Various agents contained in the guar gum, and associated conditions for providing the inhibiting and crosslinking action above described, are well known. Exemplary agents functioning to promote cross-linking, in addition to potassium dihydrogen antimonate and borax referred to above, are those which liberate borate, cuprous, calcium and aluminum ions, the inhibiting and cross-linking being promoted under different pH conditions. For example, sodium borate (borax) can be utilized at a pH of from about 5 to 6 to promote inhibition of hydration, and, as above discussed, it promotes cross-linking when the pH is increased to about 7 and somewhat higher.

\Vhen referring herein to hydration, it is meant the reaction that takes place between the guar gum and water to form a sol, and when referring to cross-linking, it is meant the cross-linking reaction that takes place between the guar gum and the particular cross-linking agent to form a gel.

As will be evident to those skilled in the art, various modifications can be made or followed, in light of the foregoing disclosure and discussion, without departing from the spirit or scope of the disclosure or from the scope of the claims.

What we claim and desire to protect by Letters Patent is:

1. In an inorganic oxidizer salt explosive composition of the aqueous slurry type, the improvement comprising a sensitizing amount of at least one alkanolamine nitrate selected from the group consisting of ethanolamine nitrates, and propanolamine nitrates, as a sensitizer component.

2. The improvement of claim 1 wherein said explosive composition is a nitrocarbonitrate.

3. A composition of claim 2 wherein said sensitizer component is at least one ethanolamine nitrate.

4. A composition of claim 3 wherein said sensitizer component is at least triethanolamine nitrate.

5. A composition of claim 2 wherein said sensitizer component is at least one propanolamine nitrate.

6. A composition of claim 5 wherein said sensitizer component is at least one tripropanolamine nitrate.

7. A composition of claim 2 containing from 3 to 30 weight percent of said alkanolamine nitrate sensitizer component.

8. A composition of claim 2 containing a supplemental sensitizer selected from the group consisting of a particulate metal, finely divided coal, a hydrocarbon oil, and dinitrotoluene.

9. A composition of claim 8 containing from 1 to 10 weight percent of said supplemental sensitizer.

10. A composition of claim 9 wherein said supplemental sensitizer is particulate aluminum.

11. A composition of claim 7 containing from 3 to 10 percent of said alkanolamine nitrate sensitizer component.

12. A composition of claim 11 containing a gas incorporated therein to provide a density of from 50 to 90 percent of the maximum.

13. A composition of claim 11 containing from 1 to 10 percent of a supplemental sensitizer selected from the group consisting of a particulate metal, finely divided coal, a hydrocarbon oil, and dinitrotoluene.

14. A composition of claim 7 containing, on a weight basis, from 8 to 25 percent water, from 40 to percent of said oxidizer salt, and from 0.2 to 5.0 percent of a thickener.

15. A composition of claim 14 containing from '10 to 25 weight percent of said alkanolamine nitrate sensitizer component.

16. A composition of claim 14 containing from 3 to 10 weight percent of said alkanolamine nitrate sensitizer component and a supplemental sensitizer selected from the group consisting of a particulate metal, finely divided coal, a hydrocarbon oil, and dinitrotoluene.

17. A composition of claim 16 wherein said supplemental sensitizer is from 3 to 7 weight percent particulate aluminum of which at least 5 weight percent is in flake form.

18. A composition of claim 14 containing from 3 to 10 weight percent of said sensitizer component and containing a gas incorporated therein to provide a density of from 50 to percent of the maximum.

19. A composition of claim 2 containing, on a weight basis, from 12 to 20 percent water, from 40 to 65 percent ammonium nitrate, from 5 to 20 percent sodium nitrate, from 0.3 to 2.0 percent guar gum in cross-linked form, and from 3 to 25 percent of said alkanolamine nitrate sensitizer component.

20. A composition of claim 1 containing the total reaction product mixture formed by reaction of an alkanolamine selected from the group consisting of ethanolamines and propanolamines with aqueous nitric acid to form said alkanolamine nitrate sensitizer component, and having a pH in the range of from about 3 to 7.

References Cited UNITED STATES PATENTS 2,965,466 12/1960 Ball 149 92 X 3,238,074 3/1966 Grifiith et al. 149-38 X 3,330,706 7/1967 Griffith 149--38 3,949,453 8/1962 De Wilde 149-47X CARL D. QUARFORTH, Primary Examiner.

S. J. LECHERT, JR., Assistant Examiner. 

